The broad aims of this project continue essentially the same, namely to investigate the various factors that govern the nature of the folding, or conformation, taken up by a protein chain which determines its biological activity, in relation to the various components of its primary structure, namely its amino acid sequence. These studies would ultimately lead to the possibility of the prediction of the conformation of a polypeptide chain, given the sequence of residues in it. One of the aims of the continued project would be to estimate the accuracy of the potential functions adopted for this purpose and to obtain more accurate functions by comparing theory and observations (x-ray, NMR, etc.) in various simple systems of increasing complexity. In particular, the conformation of peptides having mixed L and D amino acids will be studied, with special reference to their application to the case of peptide antibiotics. The structure of collagen, which has been one of the main fields of study of the principal investigator, will be refined in order to explain the biological functions of collagen. An additional new problem to be studied will be the mathematical technique of reconstruction of a three-dimensional object from its transmission shadowgraphs. This has wide application in medical radiology and in the study of viruses and other objects by electron microscopy. The conformational studies would ultimately lead to the prediction of the structure of proteins, enzymes, and antibiotics in relation to their biological activity. BIOLOGICAL REFERENCES: A. S. Kolaskar, A.V. Lakshminarayanan, K. P. Sarathy and V. Sasisekharan. The nonplanar peptide unit. Biopolymers 14, 1081-1094 (1975). M. Bansal, C. Ramakrishnan and G. N. Ramachandran. A triple-helical model for (Gly-Pro-Hyp)n with cis peptide units. Biopolymers 14, 2457-2466 (1975).